The aim of the EUROLAKES project is to formulate recommendations to EU policy arising from the management of lakes in EU. To this aim first of all it is necessary to understand the policy and legislation influencing Lake Management. This report shall give a description of relevant policies and regulations and therefore be a basis for the further research within the EUROLAKES project. A deeper analysis will take place in a further step. Finally, at the end of the project recommendations will be formulated.

The first part of this report concerns general considerations on the lakes under study and on the general problems related to mass exchanges of gases between an atmosphere and a liquid. The AIRLAC is a high capacity, high efficiency oxygenator which is capable to take water at any level in the lake and to reject it after treatment at the same level, thus preventing any vertical mixing with the other layers of the lake. In a first attempt, we have presented a possible other solution using optimised air injection at the bottom of the lake. It is a basis for comparison. The first part of this report concerns general considerations on the lakes under study and on the general problems related to mass exchanges of gases between an atmosphere and a liquid.

Please download the whole report: D15-a.pdf (809 KB)

Part II - MYRIAFLOW and HYDROBARRIER

This part of the report is the phase 4 of a study relative to technical solutions applicable to medium size lakes such as those studied in the EUROLAKES project. It is shown that the behaviour of a lake can be modified with low power consumption systems. It had been shown that other countries consider artificial actions on lakes as possible means of remediation. This is mostly the case of Canadians which have applied a number of techniques for curing and evaluation. In this report, we give some examples of application of two extra techniques, the MYRIAFLOW and the HYDROBARRIER.

Please download the whole report: D15-b.pdf (368 KB)

Part III - EUROSKIMMER

In general, the pollution in a lake will not be linked with extremely severe weather conditions, except in the case of a cargo ship wreckage. The weather conditions can be considered as calm compared to sea conditions when such accidents happen. The examples of Torrey-Canyon, Amoco-Cadix and more recently of ERIKA show that the sea state is almost always the trigger for such accidents, even though it is not the only reason in most cases.
To remove the oil thus contained, there exist some hydrophobic and oilophylic materials which can pump the oil as a sponge. These systems are available under the form of belts and are well suited for applications to industrial installations. In the same category are the surface static skimmers which can work only in perfectly calm weather conditions. We have developed in more details the principle of Cyclonet which has been developed in the 70's by SOGREAH. This small system can be simply attached by a small ship hull and can be put in operation very rapidly.

Lake shores constitute a transitional area between aquatic, terrestrial and air environ-ments. As is the case with all transitional areas (ecotones), shorelines harbour an immense biological wealth. They provide habitats for living beings that need both the aquatic environment and the terrestrial environment either simultaneously or at different periods of their life cycles. They also attract a large number of organisms that find food or shelter there, since the shores are often less accessible to terrestrial predators. With their own plant colonisation and biological wealth, shores contribute to the biological wealth of the lake itself. From the physical point of view, river and lake morphology is governed by the friability or strength of their banks and shores. Shores also constitute the last barrier before reaching the lake or river for all inflows from catchment areas. They often play a major role of entrapment and purification for both surface and subsurface flows.

Many biological and chemical processes in lakes depend either directly or indirectly on the concentration of substances dissolved in the water. This water (and its ingredients), however, is constantly moved under variable hydrological and meteorological conditions, is mixed with surrounding water or stays very long in sheltered bays, and eventually leaves the lake via outflow or evaporation. The work described in this report accordingly was aimed at the calculation of more realistic residence times using three-dimensional models under varying meteorological and hydrological conditions with application to very different lakes in shape and bathymetry. The final objective was to present recommendations on how to use 3D model applications to enable (if possible) simplified 1D box models or 2D approaches to residence times which might be of sufficient quality for management purposes.

Tributary inflow to deep European lakes is characterised mostly by higher density compared to the lake surface waters as result of the generally lower temperature regime, suspended load and partly density relevant dissolved compounds. Therefore, the river waters propagate mostly as interflows or underflows depending on the density difference. The momentum supply by the inflow and mixing between the two fluids constitute a strongly tilted internal front in the plunging phase emerging near the mouth at the surface as plunge line. Then, the river plume spreads out under buoyancy effects, mixing gradually with the lake water superposed as leakage current on the lake-inherent transient transport field. Understanding these flow processes is necessary precondition for evaluating the dispersion of nutrients and pollutants transported by the tributaries as well as the distribution of river-borne harmful matter deposited in the lake sediments below and aside the pathways of the river plumes. These dispersion phenomena have been studied for real lake and tributary configurations through numerical experiments and evaluation of synoptic measurements. The effects of varying density differences between river and lake water, of the adopted turbulence modelling scheme and of the deflection by the Coriolis force have been investigated. An important empirical account is concerned with the river-induced long term changes of the physical and limnological state for the example of Lac Léman as aftermath of anthropogenic measures in the catchment. This analysis refers mainly to the erection of hydroelectric power plants and large scale river-bed reconstruction in the past with considerable down stream effects transmitted to the lake.

Please download the whole report: D29.pdf (9,566 KB)